During the five-year Beagle expedition, Darwin shipped home 1,529 species preserved in spirit and 3,907 labelled skins, bones and other dried specimens.
In 1833, Darwin inadvertently ate a new bird species for Christmas dinner on the Beagle. When he realised, the leftovers were immediately preserved and sent home. They were later named after Darwin as the lesser rhea – Rhea darwinii.
Darwin collected fossils of extinct giant mammals, such as the giant ground sloth and the armoured Glyptodon, as well as living animals and plants.
When Darwin explored the Galapagos Islands in 1835, it was the similarities and differences between mockingbirds – not the famous finches – on different islands that made him wonder how they were related.
The first record of Darwin’s idea that all living things are related and have a common ancestor came six months after the Beagle voyage. He sketched a diagram of an evolutionary tree, its branching lines resembling the structure of an alga specimen, called Amphiroa orbignyana, that he collected in Argentina.
Darwin in north Australia was named by two of Darwin’s former shipmates, who led the Beagle’s next voyage.
King’s College London has a good summary about the voyage of the Beagle on its website.
Britannica also has an excellent history of HMS Beagle.